
1. Variations of solar output. Long term increase in luminosity • Moderate to short term changes in fusion rate and diameter • Moderate to short term surface variations
Controls of Stellar Fusion • Fuel • Pressure • Temperature • Sun shrinking about 0.1% /100 years becoming more energic
Above: Yearly-averaged sunspot numbers from 1610 to 2008. Researchers believe upcoming Solar Cycle 24 will be similar to the cycle that peaked in 1928, marked by a red arrow. Credit: NASA/MSFC
Sun Spot Cycles • Observations 527 BC • 8 – 16 years • Alternating solar polarity • 10 year cycles AD 800-900 • 10.2 year cycles 1914 – • 12 – 14 year cycles 1656-1723, 1799-1833,1870-1913
Solar Activity Index • Weighted frequency of sun spots and auroral displays • 14C formation inverse to SAI • Dates SAI # of Glaciers advancing • AD 1011-1211 1 05 3 • AD 1212-1387 95 2 • AD 1388-1586 91 6 • AD 1587-1798 81 36 • AD 1799- 1879 91 20 • AD 1880-1964 109 5 • Maunder Minimum 1645-1717 Little Ice Age
Sunspot cycle from 1700 with Dalton Minimum and expected levels.Source: Badalyan, Obridko and Sykora
The Dalton Minimum was a period of low solar activity, named for the English meteorologist John Dalton, lasting from about 1790 to 1830.[1] Like the Maunder Minimum and Spörer Minimum, the Dalton Minimum coincided with a period of lower-than-average global temperatures. The Oberlach Station in Germany, for example, experienced a 2.0° C decline over 20 years.[2] The Year Without a Summer, in 1816, also occurred during the Dalton Minimum.
2. Cosmic dust vails • Rotation (about 250,000,000 years) • Translation (130-600 Km/Sec)
Interstellar Stuff • Calculations suggest that there is lots of stuff not in observed bodies • Stars form where stuff is compressed at the leading edge of a galaxy • Not all stuff into stars • Stuff not uniformly distributed • Stuff likely to slightly obscure the sun and reduce insolation
3. Variations in Earth - Sun Relations (Astronomical Theory, Milankovitch Cycles) • One of the most popular theories • Used to explain several types of phenomena through geologic time • Can be modeled simply
Milankovitch CycleCroll- Milankovitch Cycle • Proposed by geologist James Croll (1821-1890) • “Climate and Time in their Geological Relations” 1867 • Serbian astronomer Milutin Milankovitch (1879-1958) • calculated the slow changes in the earth's orbit by careful measurements of the position of the stars • Mathematical Climatology and the Astronomical Theory of Climatic Changes1930 • Major publications 1920, 1941
Components • Earth’s Orbit • Earths Tilt • Earths Precession
Orbit Data • 2004 • Perihelion Jan 4 18 Aphelion July 5 11 • Equinoxes Mar 20 06 49 Sept 22 16 30 Solstices June 21 00 57 Dec 21 12 42 • 2005 • Perihelion Jan 2 01 Aphelion July 5 05 Equinoxes Mar 20 12 33 Sept 22 22 23 Solstices June 21 06 46 Dec 21 18 35
Orbital Data • Dates and times of aphelion and perihelion of Earth:2010-Jan-03 00-hour Earth at perihelion 0.983290 AU (91,422,023 miles or 147,098,036 km)2010-Jul-06 11-hour Earth at aphelion 1.016702 AU (94,528,559 miles or 152,096,452 km)
Eccentricity • About 100,000 years • Change in orbit shape and center • Main component 110,000 years, minor component 413,000 years • Currently more circular • Jan 3 perihelion, July 4 aphelion • 6% difference between January and July • At Maximum ellipse • 20 – 30% difference
Tilt (inclination to plane of ecliptic) • Range 21.8o to 24.4o • Period 41,000 years • Currently about midpoint
Precession (wobble) • North pole pointing at the North Star, to having the North pole pointing at the star Vega • 22,000 year cycle is composed of a 19,000 cycle and a 23,000 year cycle).
4. Atmospheric Conditions • Composition • N2, O2, Greenhouse Gasses (H2O, • Particluates
Dust Veil Index • DVI = 0.97 Rmax Emax Tmo • DVI = 52.5 Tdmax Emax Tmo • DVI = 4.4 Q Emax Tmo